Cell division and morphogenesis in various plant cells (particularly green algae) are being studied, with emphasis on fine structure. Comparative studies on mitosis and cytokinesis have yielded phylogenetic information on the organisms concerned, and also on the way the mitotic and cytokinetic systems have altered during evolution. High voltage electron microscopy and treatment of mitotic spindles with drugs are yielding new information on the structure and perhaps the function of the mitotic apparatus in certain green algae. Morphogenesis, and particularly control of cell form, is being studied in desmids. This latter work is approaching the problem from several directions, including an ultrastructural analysis of dividing cells, the effects of inhibitors of RNA and protein synthesis on morphogenesis, and attempts to obtain artificially produced morphological mutants. At present we are attempting to define the system carefully, particularly in terms of the reproducibility of experimental investigations.